/**
 * filesize
 *
 * @copyright 2019 Jason Mulligan <jason.mulligan@avoidwork.com>
 * @license BSD-3-Clause
 * @version 6.0.1
 */
 
const b = /^(b|B)$/,
      symbol = {
        iec: {
          bits: ["b", "Kib", "Mib", "Gib", "Tib", "Pib", "Eib", "Zib", "Yib"],
          bytes: ["B", "KiB", "MiB", "GiB", "TiB", "PiB", "EiB", "ZiB", "YiB"]
        },
        jedec: {
          bits: ["b", "Kb", "Mb", "Gb", "Tb", "Pb", "Eb", "Zb", "Yb"],
          bytes: ["B", "KB", "MB", "GB", "TB", "PB", "EB", "ZB", "YB"]
        }
      },
      fullform = {
        iec: ["", "kibi", "mebi", "gibi", "tebi", "pebi", "exbi", "zebi", "yobi"],
        jedec: ["", "kilo", "mega", "giga", "tera", "peta", "exa", "zetta", "yotta"]
      };

/**
 * filesize
 *
 * @method filesize
 * @param  {Mixed}   arg        String, Int or Float to transform
 * @param  {Object}  descriptor [Optional] Flags
 * @return {String}             Readable file size String
 */
function filesize (arg, descriptor = {}) {
  let result = [],
    val = 0,
    e, base, bits, ceil, full, fullforms, locale, localeOptions, neg, num, output, round, unix, separator, spacer, standard, symbols;

  if (isNaN(arg)) {
    throw new TypeError("Invalid number");
  }

  bits = descriptor.bits === true;
  unix = descriptor.unix === true;
  base = descriptor.base || 2;
  round = descriptor.round !== void 0 ? descriptor.round : unix ? 1 : 2;
  locale = descriptor.locale !== void 0 ? descriptor.locale : "";
  localeOptions = descriptor.localeOptions || {};
  separator = descriptor.separator !== void 0 ? descriptor.separator : "";
  spacer = descriptor.spacer !== void 0 ? descriptor.spacer : unix ? "" : " ";
  symbols = descriptor.symbols || {};
  standard = base === 2 ? descriptor.standard || "jedec" : "jedec";
  output = descriptor.output || "string";
  full = descriptor.fullform === true;
  fullforms = descriptor.fullforms instanceof Array ? descriptor.fullforms : [];
  e = descriptor.exponent !== void 0 ? descriptor.exponent : -1;
  num = Number(arg);
  neg = num < 0;
  ceil = base > 2 ? 1000 : 1024;

  // Flipping a negative number to determine the size
  if (neg) {
    num = -num;
  }

  // Determining the exponent
  if (e === -1 || isNaN(e)) {
    e = Math.floor(Math.log(num) / Math.log(ceil));

    if (e < 0) {
      e = 0;
    }
  }

  // Exceeding supported length, time to reduce & multiply
  if (e > 8) {
    e = 8;
  }

  if (output === "exponent") {
    return e;
  }

  // Zero is now a special case because bytes divide by 1
  if (num === 0) {
    result[0] = 0;
    result[1] = unix ? "" : symbol[standard][bits ? "bits" : "bytes"][e];
  } else {
    val = num / (base === 2 ? Math.pow(2, e * 10) : Math.pow(1000, e));

    if (bits) {
      val = val * 8;

      if (val >= ceil && e < 8) {
        val = val / ceil;
        e++;
      }
    }

    result[0] = Number(val.toFixed(e > 0 ? round : 0));

    if (result[0] === ceil && e < 8 && descriptor.exponent === void 0) {
      result[0] = 1;
      e++;
    }

    result[1] = base === 10 && e === 1 ? bits ? "kb" : "kB" : symbol[standard][bits ? "bits" : "bytes"][e];

    if (unix) {
      result[1] = standard === "jedec" ? result[1].charAt(0) : e > 0 ? result[1].replace(/B$/, "") : result[1];

      if (b.test(result[1])) {
        result[0] = Math.floor(result[0]);
        result[1] = "";
      }
    }
  }

  // Decorating a 'diff'
  if (neg) {
    result[0] = -result[0];
  }

  // Applying custom symbol
  result[1] = symbols[result[1]] || result[1];

  if (locale === true) {
    result[0] = result[0].toLocaleString();
  } else if (locale.length > 0) {
    result[0] = result[0].toLocaleString(locale, localeOptions);
  } else if (separator.length > 0) {
    result[0] = result[0].toString().replace(".", separator);
  }

  // Returning Array, Object, or String (default)
  if (output === "array") {
    return result;
  }

  if (full) {
    result[1] = fullforms[e] ? fullforms[e] : fullform[standard][e] + (bits ? "bit" : "byte") + (result[0] === 1 ? "" : "s");
  }

  if (output === "object") {
    return {value: result[0], symbol: result[1]};
  }

  return result.join(spacer);
}

filesize.partial = opt => arg => filesize(arg, opt);

export default filesize;
